1. Field of the Invention
The present invention relates to a technique of manufacturing a Silicon on Quartz (SOQ) substrate where a single crystal silicon thin film is formed on a quartz substrate.
2. Description of the Related Art
In recent years, a Silicon on Sapphire (SOS) substrate has received attentions as a radio-frequency (RF) device substrate because a sapphire lattice constant is close to that of single crystal silicon, so heteroepitaxial growth can proceed and in addition, the substrate is suitable for fabrication of an RF device.
As compared with a Metal Oxide Semiconductor (MOS) transistor fabricated on a silicon substrate, a MOS transistor having an SOS structure is advantageous in that a power of an RF signal that leaks to a ground side through a sapphire substrate (power loss/signal loss) is small because of a small source-ground/drain-ground stray capacitance of the transistor.
On the other hand, the sapphire substrate has a problem in that the substrate is very expensive and it is difficult to increase its diameter. As a conceivable alternative to the sapphire substrate, there is a quartz substrate that is inexpensive and can increase its diameter as compared with the sapphire substrate. However, if the quartz substrate is used as a Silicon on Insulator (SOI) substrate, since epitaxial growth cannot proceed in a single crystal silicon film on the quartz substrate, it is necessary to transfer the single crystal silicon film onto the quartz substrate by a so-called “bonding method” (see Japanese Patent No. 3048201 and A. J. Auberton-Herve et al., “SMART CUT TECHNOLOGY: INDUSTRIAL STATUS of SOI WAFER PRODUCTION and NEW MATERIAL DEVELOPMENTS” (Electrochemical Society Proceedings Volume 99-3 (1999) p. 93-106), for example).